Phase Change Charging Interface for Implanted Neurostimulator Heat Control

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Solution Overview

Problem

Current implantable medical device charging systems are inefficient, requiring frequent and lengthy charging sessions, which can be uncomfortable for patients and lead to increased heat generation, causing skin temperature limits to be reached quickly, thereby reducing the system's usability and patient satisfaction.

Innovation Solution

Incorporating a phase change material into the charging device that absorbs heat generated by the coil, allowing the device to maintain a conformable interface and extend the time to reach thermal thresholds, along with a heat reduction assembly and a conformable thermal ground plane to manage heat dissipation and improve comfort and efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If wireless energy transfer is used to charge implantable medical devices, then charging convenience is improved, but heat generation increases causing skin temperature limits to be reached quickly

Engineering Contradiction:

Improvecharging convenienceVSAvoidskin temperature

Core Design Contradiction:

Ease of operationVSTemperature

Solution Approach 1:

A phase change material is introduced as an intermediary between the charging device and the patient's skin. This material absorbs excess heat generated during wireless energy transfer through phase transition (melting), preventing direct heat transfer to the skin and allowing longer charging sessions without reaching temperature limits.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The charging device utilizes a phase change material that transitions from solid to liquid state at a specific melting point. During charging, the material absorbs thermal energy through this phase transition, effectively managing heat accumulation and extending the duration before skin temperature limits are reached.

Inventive Principle:

Principle #36Phase transitions

2Productivity

If charging power is increased to reduce charging time, then productivity is improved, but heat generation increases reducing usability

Engineering Contradiction:

Improvecharging speedVSAvoidusability

Core Design Contradiction:

ProductivityVSEase of operation

Solution Approach 1:

The harmful heat generated by high-power charging is converted into a beneficial thermal management solution. The phase change material absorbs this excess heat through phase transition, transforming the harmful thermal energy into latent heat of fusion, thereby enabling high-power charging without compromising patient comfort or usability.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Loss of time

If charging session duration is extended to improve efficiency, then loss of time is reduced, but heat accumulation increases causing discomfort

Engineering Contradiction:

Improvecharging session durationVSAvoidheat accumulation

Core Design Contradiction:

Loss of timeVSTemperature

Solution Approach 1:

The phase change material provides extended heat absorption capacity through its phase transition process. As charging continues, the material progressively absorbs heat while maintaining a relatively constant temperature during the phase change, enabling longer charging sessions without proportional increases in skin temperature or patient discomfort.

Inventive Principle:

Principle #36Phase transitions

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution extends charging session duration, reduces heat load on the patient, and enhances user comfort by maintaining a stable temperature, thereby improving the overall efficiency and effectiveness of the charging process for implantable medical devices.

Implementation Method 1

a phase change material. Any of the aspects herein, wherein the phase change material changes between a solid state and a fluid state at a temperature range of about 35 degrees Celsius to about 41 degrees Celsius

Methodology Applied

Scientific EffectPhase change: Phase Change

Implementation Method 2

the phase change material absorbs at least a portion of heat generated by the coil

Methodology Applied

Scientific EffectHeat absorption: Latent Heat

Implementation Method 3

at least a portion of the ground plane includes a thermal conductive material

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS20230310869A1Removable phase change material to produce conformable interface for recharging an implanted neurostimulator

Publication Date: 2023.10.05 MEDTRONIC INC

AI summary

A charging device includes a coil configured to wirelessly transfer energy to an implantable medical device. The charging device includes a phase change material. The charging device may include a ground plane. The phase change material is incorporated in the charging device, and a flexibility of the charging device is associated with a state of the phase change material. The ground plane is conformable to one or more surfaces of a target subject. The charging device may include a heat reduction assembly. The heat reduction assembly includes a material disposed in contact with the coil. The phase change material absorbs at least a portion of heat generated by the coil.